JPS644792Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial field of application) The present invention has a work platform attached to the tip of a hoisting boom that is mounted on a base so that it can be raised and lowered in the vertical direction and moved up and down as needed by a hoisting cylinder. The upper leveling cylinder is installed so that it can be raised and lowered in the vertical direction, and an upper leveling cylinder is installed between the work platform and the tip of the lowering boom.
Further, a lower leveling cylinder is installed between the base end of the hoisting boom and the base, and the extension side chamber of the upper leveling cylinder and the extension side chamber of the lower leveling cylinder are connected by a first oil passage. A first sealed circuit is connected to the compression side chamber of the upper leveling cylinder and the contraction side chamber of the lower leveling cylinder by a second oil passage.
A sealed circuit is configured respectively, and the upper leveling cylinder and the lower leveling cylinder are expanded and contracted in synchronization with each other in conjunction with the raising and lowering operation of the hoisting boom, so that the posture of the workbench is always kept constant by the upper leveling cylinder. The present invention relates to a leveling device for a work machine with a hoisting boom that is held in place.

(Prior Art) In the conventional work machine with a hoisting boom equipped with this type of leveling device, for example, in the aerial work vehicle shown in FIG. 2, when the hoisting cylinder 105 is extended to raise the hoisting boom 103, boom 1
03, the extension operation of the lower leveling cylinder 107 and the contraction operation of the upper leveling cylinder 106 progress synchronously, and the workbench 104
is raised while maintaining the horizontal state. In this case, for example, if the extension operation of the undulating cylinder 105 is connected even though the upper leveling cylinder 106 has reached the fully retracted position, the second sealed circuit 122 There is a risk that the hydraulic pressure inside the unit will rise abnormally, causing a dangerous situation such as damage to the hydraulic hose.

For this reason, in conventional leveling devices,
Relief valves 120, 120 are provided in the first oil passage 111 and the second oil passage 112, respectively, and when abnormal pressure occurs, a part of the pressure oil is discharged to the outside by the relief action of the relief valves 120, 120, thereby reducing the pressure. The pressure rise was kept below the set pressure.

However, in this way, the first and second oil passages 111,
112 and relief valves 120 and 120, respectively.
, there is a limit to the sealing performance of the relief valve 120 itself (that is, it is difficult to completely seal each sealed circuit 111, 112), and the Since there are differences in the degree of sealing performance, if the leveling operation is repeated, the amount of hydraulic oil sealed in each sealed circuit 111, 112 will change, and the posture of the workbench 104 will gradually change. I had a problem with it coming.

(Purpose of the invention) In view of the problems of conventional leveling devices as described above, the present invention reliably prevents abnormal pressure from occurring within the sealed circuit, and maintains good leveling accuracy over a long period of time. The object of this invention is to provide a leveling device for a working machine with a hoisting boom, which is designed to improve safety and reliability.

(Structure of the invention) The leveling device for a work machine with a hoisting boom according to the present invention has the basic configuration as shown in the header. A pressure detection device is provided to detect the hydraulic oil pressure in the circuit, and when the hydraulic oil pressure in the first sealed circuit or the hydraulic oil pressure in the second sealed circuit reaches a preset pressure or higher, The present invention is characterized in that it is configured to forcibly stop the hoisting operation of the hoisting boom based on the output signal from the pressure detection device.

(Example) Hereinafter, the leveling device of the present invention will be explained based on an example. Fig. 1 shows an aerial work vehicle Z equipped with a leveling device according to an embodiment of the present invention. This aerial work vehicle Z has a three-stage telescoping hoisting boom 3 attached to a swivel platform (base) 2 attached to the loading platform of a vehicle 1 so as to be able to be lifted up and down in the vertical direction. A workbench 4 is attached to the tip end 3b of the hoisting boom 3 so that it can be raised and lowered in the vertical direction. This workbench 4 is raised or lowered by the telescoping movement of an upper leveling cylinder 6 attached between the workbench 4 and the tip end 3b of the hoisting boom 3.

On the other hand, a lower leveling cylinder 7 is installed between the base end 3a of the hoisting boom 3 and the swivel base 2. The extension side chamber 7a of the lower leveling cylinder 7 and the extension side chamber 6a of the upper leveling cylinder 6 are connected by a first oil passage 11, and a first sealed circuit 2
1, and the contraction side chamber 7b of the lower leveling cylinder 7 and the contraction side chamber 6b of the upper leveling cylinder 6 are connected by a second oil passage 12 to constitute a second sealed circuit 22. Further, the first oil passage 11 and the second oil passage 12 are connected to a leveling adjustment switching valve 17 via stop valves 18, 18, respectively. The stop valves 18, 18 are opened only when adjusting the leveling, that is, when adjusting the posture of the workbench 4, and are closed in other cases to ensure the sealing performance of the first and second sealed circuits 21, 22. It is becoming increasingly important to ensure that Also, in Fig. 2, the symbol 1
6 and 16 are the first oil passage 11 or the second oil passage 12
This is a pilot check valve provided in the first oil passage 11 and the second oil passage 12 in order to prevent the workbench 4 from falling suddenly in the event of damage.

On the other hand, the undulation cylinder 5 is expanded and contracted as appropriate by switching control of the electromagnetic switching valve 10. Moreover, the first solenoid coil 13A of this electromagnetic switching valve 10
and the second solenoid coil 13B are selectively energized by switching the hoisting changeover switch 9 to the lodging side contact 9a and the rising side contact 9b by the hoisting operation lever 8, respectively, and the electromagnetic switching valve 10 is switched to the first solenoid coil 13B. 1
It can be set to the valve position 10a or the second valve position 10b. Furthermore, among the control circuits of the respective solenoid coils 13A and 13B, the control circuit 2 of the first solenoid coil 13A
3 includes a first pressure switch 14 that opens when the oil pressure in the first sealed circuit 21 reaches a predetermined pressure or higher and acts to de-energize the first solenoid coil 13A; 13
A second pressure switch 15 is provided in the control circuit 24 of the second sealed circuit 22, which opens when the oil pressure in the second sealed circuit 22 reaches a predetermined pressure or higher, and acts to de-energize the second solenoid coil 13B. ing.

In this way, the control circuits 23 and 24 of the electromagnetic switching valve 10 for up-and-down operation are connected to the sealed circuit 2 for leveling.
Pressure switch 1 that operates according to the internal pressure of 1 and 22
4 and 15, it is possible to reliably prevent abnormal pressure from occurring within the sealed circuits 21 and 22. That is, for example, when the hoisting boom 3 is raised, the lower leveling cylinder 7 extends and the upper leveling cylinder 6 contracts as the hoisting angle of the hoisting boom 3 increases, so that the workbench 4 remains in a horizontal position. However, in this case,
For example, if the extension operation of the undulating cylinder 5 is still connected even though the upper leveling cylinder 6 has reached the fully retracted position, the pressure of the hydraulic oil in the second sealed circuit 22 will rise rapidly. However, in the case of this embodiment, when the hydraulic pressure reaches the set pressure, the second
The pressure switch 15 opens, the excitation of the second solenoid coil 13B of the electromagnetic switching valve 10 is released, the electromagnetic switching valve 10 returns to the neutral position, and the undulating cylinder 5
The extension operation of is forced to stop. Therefore, the hydraulic pressure within the second sealed circuit 22 is prevented from rising above the set pressure, and its safety is ensured. In addition, when the hoisting boom 3 is lowered, the first pressure switch 14 is activated, contrary to when the hoisting boom 3 is raised.
This ultimately prevents the hydraulic pressure within the sealed circuit 21 from rising above the set pressure.

In the above embodiment, the pressure inside the first and second sealed circuits 21 and 22 is detected, and based on this, the operation of the undulation cylinder 5 is stopped by electrical means. In other embodiments, for example, a hydraulic response type (hydraulic pilot type) switching valve operated by the hydraulic pressure in the sealed circuits 21 and 22 is provided in the hydraulic circuit of the luffing cylinder 5 to control the operation of the luffing cylinder 5. It is also possible to stop it using a hydraulic control method.

(Effect of the invention) The leveling device for the work machine with a hoisting boom of the present invention detects the hydraulic oil pressure in the sealed circuit formed between the upper leveling cylinder and the lower leveling cylinder in the control system of the hoisting cylinder. A pressure detection device is provided, and when the hydraulic oil pressure in the sealed circuit reaches a set pressure or more due to the up-and-down operation of the up-and-down cylinder, the up-and-down operation of the up and down cylinder is forced based on a signal from the pressure detection device. Since the device is stopped automatically, abnormal pressure is reliably prevented from being generated in the sealed circuit, which has the effect of improving the safety and reliability of the device.

Furthermore, since the hydraulic fluid pressure in the sealed circuit is detected and predetermined abnormal pressure prevention operations are performed based on this, a relief valve is installed in the sealed circuit, and the relief action of the relief valve causes the seal to be sealed. Unlike conventional leveling devices that prevent abnormal pressure from occurring within the circuit, there is no risk that the sealing performance of the sealed circuit will be compromised, and the posture of the workbench can be maintained at the set posture for a long period of time. This has the practical effect of improving the leveling performance.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram of a vehicle for aerial work equipped with a leveling device according to an embodiment of the present invention, and FIG. 2 is a diagram of the entire system of a vehicle for aerial work equipped with a leveling device of a conventional structure. 2... Base, 3... Lifting boom, 4... Work platform, 5... Lifting cylinder, 6... Upper leveling cylinder, 7... Lower leveling cylinder, 11
...First oil path, 12...Second oil path, 14, 15...
...Pressure detection device, 21, 22... Sealed circuit.

Claims (1)

[Scope of utility model registration request] A workbench 4 is attached to the tip portion 3b of a hoisting boom 3, which is attached to the base 2 so as to be able to be raised and lowered in the vertical direction, and is moved up and down as appropriate by a luffing cylinder 5, and furthermore, the workbench 4 is and the upper leveling cylinder 6 between the tip end 3b of the hoisting boom 3, and the base end 3a of the hoisting boom 3.
A lower leveling cylinder 7 is installed between the upper leveling cylinder 6 and the base 2, and the extension side chamber 6a of the upper leveling cylinder 6 and the extension side chamber 7a of the lower leveling cylinder 7 are connected by a first oil passage 11. 1 sealing circuit 21, and the contraction side chamber 6b of the upper leveling cylinder 6 and the contraction side chamber 7b of the lower leveling cylinder 7 are connected to the second oil passage 12.
are connected to form the second sealed circuit 22,
In conjunction with the raising and lowering movement of the hoisting boom 3, the upper leveling cylinder 6 and the lower leveling cylinder 7 are synchronously expanded and contracted so as to contradict each other, and the posture of the workbench 4 is always maintained at a constant posture by the upper leveling cylinder 6. In this leveling device for a work machine with a hoisting boom, the control system of the hoisting cylinder 5 includes the first sealed circuit 2.
1 and the second sealed circuit 22 are provided, and pressure detection devices 14 and 15 are provided to detect the hydraulic oil pressure in the first sealed circuit 21 or the second sealed circuit 22.
When the hydraulic oil pressure within reaches a preset pressure or higher, the hoisting operation of the hoisting boom 3 is forcibly stopped based on output signals from the pressure detection devices 14 and 15. A leveling device for a work machine with a hoisting boom, characterized in that: